Funds are requested for the purchase of a BIAcore Surface Plasmon Resonance (SPR) Biosensor system for measuring and characterizing a range of intermolecular interactions. This instrument is a fully automated system for the detection of binding interactions between molecules immobilized on the surface of a biosensor chip and solution phase ligands of molecular weights in excess of 200 Da and at a lower concentration limit of 1 pM in real time without the use of optically detectable or radioactive labels. The detection principle relies on the optical phenomenon of SPR, which detects changes in the refractive index of the solution close to the surface of the sensor chip. This is in turn directly related to the concentration of the interacting molecule bound to the surface layer of the sensor chip. The instrument is equipped with four separate flow cells that allow analyses with samples volumes of 20-80 muI under precisely controlled conditions of temperature and flow rate. Kinetic measurements can be made for interactions with association rate constants in the range 103-107M-1S-1. This instrument will be used primarily by a small group of NIH-supported Investigators in the School of Medicine at the State University of New York at Stony Brook. This type of instrument is not currently available at this institution. The instrument will be housed in a dedicated laboratory, maintained and overseen by a properly trained technician and an appropriate budget will be apportioned for the supplies and consumable items necessary to ensure efficient operation. An advisory committee will be responsible for controlling access to the instrument. The projected major users of the instrument are engaged in research in the areas of cell signaling, virology and molecular carcinogenesis. A group of secondary investigators will also benefit from access to this technology. These include workers with interests in measuring interactions of DNA polymerases, transcription factors and DNA repair proteins with normal and damaged nuclear and mitochondrial DNA, in the interaction between karyophiles and the transport components of the nuclear pore complex, in the interaction of high density lipoprotein and the scavenger receptor, interaction between apolipoproteinE and amyloid protein beta-peptide and in measuring G-protein effector interactions and protein kinase interactions with substrate and scaffold proteins involved in regulation of G-protein coupled receptor signaling. All of the investigators involved in this proposal hold NIH peer reviewed research grants including R29, R37, and RO1 awards. Several of the applicants are engaged in collaborative projects supported by muti- investigator awards.